A Fractographic Study of Bending/Torsion Fatigue Failure in Metallic Materials with Protective Surface Layers

<div>Initiation sites in specimens with thermal barrier coatings subjected to (a) bending (<svg height="9.16851pt" id="M35" style="vertical-align:-0.2063904pt" version="1.1" viewbox="-0.0498162 -8.96212 30.3161 9.16851" width="30.3161pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M669 636L663 650H260C230 650 221 652 208 675H186C177 621 162 548 144 481L173 479C195 534 211 560 226 578C248 604 266 615 373 615H544C460 511 114 112 23 16L31 0H561C577 34 611 135 622 170L594 182C566 125 544 88 515 65C481 38 416 35 319 35C249 35 197 37 152 41C270 184 542 501 669 636Z" id="g113-91"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="692" vert-adv-y="692"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,12.628,0)"><path d="M535 323V373H52V323H535ZM535 138V188H52V138H535Z" id="g117-34"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="587" vert-adv-y="587"></glyph.data></g><g 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d="M462 177V227H365V632H320C217 496 116 350 21 208V177H284V109C284 43 280 38 190 31V0H451V31C369 38 365 43 365 108V177H462ZM284 227H88C155 336 218 430 282 519H284V227Z" id="g50-53"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="487" vert-adv-y="487"></glyph.data></g></svg> cycles) and (b) combined bending-torsion (<svg height="9.16851pt" id="M37" style="vertical-align:-0.2063904pt" version="1.1" viewbox="-0.0498162 -8.96212 45.818 9.16851" width="45.818pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M669 636L663 650H260C230 650 221 652 208 675H186C177 621 162 548 144 481L173 479C195 534 211 560 226 578C248 604 266 615 373 615H544C460 511 114 112 23 16L31 0H561C577 34 611 135 622 170L594 182C566 125 544 88 515 65C481 38 416 35 319 35C249 35 197 37 152 41C270 184 542 501 669 636Z" id="g113-91"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="692" 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Advances in Materials Science and Engineering

fig7

Figure 7

Figure 7: A Fractographic Study of Bending/Torsion Fatigue Failure in Metallic Materials with Protective Surface Layers 